1. Field of the Invention
The invention relates to a fuel injection control apparatus and method for an in-cylinder injection type internal combustion engine, and particularly, to an improvement in a fuel injection control mechanism operated upon start-up of the internal combustion engine.
2. Description of Related Art
Conventionally the fuel injection control apparatus of the aforementioned type has been disclosed in JP-A-8-319865. The apparatus disclosed in JP-A-8-319865 is structured to obtain a fuel injection start timing that allows the required fuel injection time period to be secured upon start-up of the engine based on the injection completion timing set in accordance with the operating state of the engine. Upon cold start of the engine, the apparatus allows to set the injection start timing during an exhaust stroke such that the quantity of the fuel required for the cold start is injected into the cylinder.
In the apparatus disclosed in JP-A-8-319865, if the fuel injection completion timing deviates from the crank angle range that allows injection of the fuel owing to the increase in the engine speed, the fuel injection valve is forcibly closed to interrupt the fuel injection so as to prevent the reverse flow of the residual gas in the cylinder to pass through the fuel injection valve.
The aforementioned apparatus disclosed in JP-A-8-319865 is capable of setting the injection start timing during the exhaust stroke upon cold start of the internal combustion engine so as to inject the fuel by the quantity required for the start-up. In this case, however, when the fuel injection completion timing deviates from the crank angle range that allows the fuel injection, the fuel injection is forcibly interrupted. This may cause the failure in injection of the required quantity of the fuel. In this apparatus, even if the injection start timing can be set during the exhaust stroke at the cold start of the engine, the quantity of the fuel required for the start-up cannot always be injected.
In the aforementioned case, it is difficult to complete the start-up of the engine at the cold state. The fuel injection for the start-up of the engine will be repeatedly performed. Especially in the start-up of the engine, the rate of the fuel subjected to the combustion to the fuel subjected to the injection into the cylinder becomes small. So the concentration of the fuel that is not combusted in the cylinder of the engine is increased. This may cause the spark plug to be covered with the fuel or smoldered with high possibility. Accordingly it becomes further difficult to start the engine.